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Quotations from Aristotle are often cited by Bekker numbers, which are keyed to the original Greek and therefore independent of the translation used. In this lemma quotes are arranged by Bekker numbers (as far as possible).

My lectures are published and not published; they will be intelligible to those who heard them, and to none beside.

Of things said without any combination, each signifies either substance or quantity or qualification or a relative or where or when or being-in-a-position or having or doing or being affected. To give a rough idea, examples of substance are man, horse; of quantity: four-foot, five-foot; of qualification: white, grammatical; of a relative: double, half, larger; of where: in the Lyceum, in the market-place; of when: yesterday, last-year; of being-in-a-position: is-lying, is sitting; of having: has-shoes-on, has-armour-on; of doing: cutting, burning; of being-affected: being-cut, being-burned.

Knowledge of the fact differs from knowledge of the reason for the fact.

I. 13, 78a.22

The premisses of demonstrative knowledge must be true, primary, immediate, more knowable than and prior to the conclusion, which is further related to them as effect to cause... The premisses must be the cause of the conclusion, more knowable than it, and prior to it; its causes, since we posses scientific knowledge of a thing only when we know its cause; prior, in order to be causes; antecedently known, this antecedent knowledge being not our mere understanding of the meaning, but knowledge of the fact as well. Now 'prior' and 'more knowable' are ambiguous terms, for there is a difference between what is prior and more knowable in the order of being and what is prior and knowable to man. I mean that objects nearer to sense are prior and more knowable to man; objects without qualification prior and more knowable are those further from sense. Now the most universal causes are furthest from sense and particular causes are nearest to sense, and they are thus exactly opposed to each other.

I. 2, 71b.9 sqq

We may assume the superiority ceteris paribus [all things being equal] of the demonstration which derives from fewer postulates or hypotheses—in short from fewer premisses; for... given that all these are equally well known, where they are fewer knowledge will be more speedily acquired, and that is a desideratum. The argument implied in our contention that demonstration from fewer assumptions is superior may be set out in universal form...

The natural way of doing this [seeking scientific knowledge or explanation of fact] is to start from the things which are more knowable and obvious to us and proceed towards those which are clearer and more knowable by nature; for the same things are not 'knowable relatively to us' and 'knowable' without qualification. So in the present inquiry we must follow this method and advance from what is more obscure by nature, but clearer to us, towards what is more clear and more knowable by nature. Now what is to us plain and obvious at first is rather confused masses, the elements and principles of which became known to us by later analysis...

The bodies of which the world is composed are solids, and therefore have three dimensions. Now, three is the most perfect number,—it is the first of numbers, for of one we do not speak as a number, of two we say both, but three is the first number of which we say all. Moreover, it has a beginning, a middle, and an end.

I. 1. as translated by William Whewell and as quoted by Florian Cajori, A History of Physics in its Elementary Branches (1899) as Aristotle's proof that the world is perfect.

...suppose α without weight, but β possessing weight; and let α pass over space γδ, but β in the same time pass over a space γε,—for that which has weight will be carried through the larger space. If now the heavy body be divided in the proportion that space γε bears to γδ, ... and if the whole is carried through the whole space γε, then it must be that a part in the same time would be carried through γδ...

Book III Ch. II as quoted by Florian Cajori (1899), as Aristotle's explanation of why bodies fall quicker in exact proportion to their weight.

That body is heavier than another which, in an equal bulk, moves downward quicker.

Sound is the motion of that which is able to be moved, after the manner in which those things are moved, that rebound from smooth bodies, when any one strikes them. Not every thing... sounds... but it is necessary, that the body which is struck should be equable, that the air may collectively rebound, and be shaken. The differences, however, of bodies which sound, are manifested in the sound, which is in energy; for, as colours are not perceived without light, so neither are the sharp and the flat perceived without sound. But these things are asserted metaphorically, from those which pertain to the touch; for the sharp moves the sense much in a short time, but the flat a little in a long time. The sharp, therefore, is not rapid, and the flat slow; but such a motion is produced of the one, on account of celerity, and of the other on account of slowness, that, also, which is perceived in the touch, appears to be analogous to the acute and obtuse, for the acute, as it were, stings; but the obtuse, as it were, impels: because the one moves in a short, but the other in a long time. Hence it happens that the one is swift but the other slow. Let it therefore be thus determined concerning sound.

It is not necessary to ask whether soul and body are one, just as it is not necessary to ask whether the wax and its shape are one, nor generally whether the matter of each thing and that of which it is the matter are one. For even if one and being are spoken of in several ways, what is properly so spoken of is the actuality.

But voice is a certain sound of that which is animated; for nothing inanimate emits a voice; but they are said to emit a voice from similitude, as a pipe, and a lyre, and such other inanimate things, have extension, modulation, and dialect; for thus it appears, because voice, also, has these.

We should venture on the study of every kind of animal without distaste; for each and all will reveal to us something natural and something beautiful.

Book I, 645a.21

The essential nature (concerning the soul) cannot be corporeal, yet it is also clear that this soul is present in a particular bodily part, and this one of the parts having control over the rest (heart).

Nature flies from the infinite, for the infinite is unending or imperfect, and Nature ever seeks an end.

Book I, 715b.15

Concerning the generation of animals akin to them, as hornets and wasps, the facts in all cases are similar to a certain extent, but are devoid of the extraordinary features which characterize bees; this we should expect, for they have nothing divine about them as the bees have.

Book III, 761a.2

Just as it sometimes happens that deformed offspring are produced by deformed parents, and sometimes not, so the offspring produced by a female are sometimes female, sometimes not, but male, because the female is as it were a deformed male.

All men by nature desire to know. An indication of this is the delight we take in our senses; for even apart from their usefulness they are loved for themselves; and above all others the sense of sight. For not only with a view to action, but even when we are not going to do anything, we prefer sight to almost everything else. The reason is that this, most of all the senses, makes us know and brings to light many differences between things.

Book I, 980a.21: Opening paragraph of Metaphysics

Variant: All men by nature desire knowledge.

The first sentence is in the Oxford Dictionary of Scientific Quotations (2005), 21:10

If, then, God is always in that good state in which we sometimes are, this compels our wonder; and if in a better this compels it yet more. And God is in a better state. And life also belongs to God; for the actuality of thought is life, and God is that actuality; and God's self-dependent actuality is life most good and eternal.

Book XII, 1072b.24

Those who assert that the mathematical sciences say nothing of the beautiful or the good are in error. For these sciences say and prove a great deal about them; if they do not expressly mention them, but prove attributes which are their results or definitions, it is not true that they tell us nothing about them. The chief forms of beauty are order and symmetry and definiteness, which the mathematical sciences demonstrate in a special degree.

If there is some end of the things we do, which we desire for its own sake, clearly this must be the good. Will not knowledge of it, then, have a great influence on life? Shall we not, like archers who have a mark to aim at, be more likely to hit upon what we should? If so, we must try, in outline at least, to determine what it is.

Book I, 1094a.18

It is the mark of an educated man to look for precision in each class of things just so far as the nature of the subject admits; it is evidently equally foolish to accept probable reasoning from a mathematician and to demand from a rhetorician scientific proofs.

Book I, 1094b.24

The life of money-making is one undertaken under compulsion, and wealth is evidently not the good we are seeking; for it is merely useful and for the sake of something else.

Book I, 1096a.5

Piety requires us to honor truth above our friends.

Book I, 1096a.16

Life seems to be common even to plants, but we are seeking what is peculiar to man. Let us exclude, therefore, the life of nutrition and growth. Next there would be a life of perception, but it also seems to be common even to the horse, the ox, and every animal. There remains, then, an active life of the element that has a rational principle; of this, one part has such a principle in the sense of being obedient to one, the other in the sense of possessing one and exercising thought. And, as "life of the rational element" also has two meanings, we must state that life in the sense of activity is what we mean; for this seems to be the more proper sense of the term. Now if the function of man is an activity of soul which follows or implies a rational principle, and if we say "so-and-so" and "a good so-and-so" have a function which is the same in kind, e.g. a lyre, and a good lyre-player, and so without qualification in all cases, eminence in respect of goodness being added to the name of the function (for the function of a lyre-player is to play the lyre, and that of a good lyre-player is to do so well): if this is the case, and we state the function of man to be a certain kind of life, and this to be an activity or actions of the soul implying a rational principle, and the function of a good man to be the good and noble performance of these, and if any action is well performed when it is performed in accordance with the appropriate excellence: if this is the case, human good turns out to be activity of soul in accordance with virtue, and if there are more than one virtue, in accordance with the best and most complete.
But we must add "in a complete life." For one swallow does not make a summer, nor does one day; and so too one day, or a short time, does not make a man blessed and happy.

Let this serve as an outline of the good; for we must presumably first sketch it roughly, and then later fill in the details. But it would seem that any one is capable of carrying on and articulating what has once been well outlined, and that time is a good discoverer or partner in such a work; to which facts the advances of the arts are due; for any one can add what is lacking. And we must also remember what has been said before, and not look for precision in all things alike, but in each class of things such precision as accords with the subject-matter, and so much as is appropriate to the inquiry. For a carpenter and a geometer investigate the right angle in different ways; the former does so in so far as the right angle is useful for his work, while the latter inquires what it is or what sort of thing it is; for he is a spectator of the truth. We must act in the same way, then, in all other matters as well, that our main task may not be subordinated to minor questions. Nor must we demand the cause in all matters alike; it is enough in some cases that the fact be well established, as in the case of the first principles; the fact is the primary thing or first principle. Now of first principles we see some by induction, some by perception, some by a certain habituation, and others too in other ways. But each set of principles we must try to investigate in the natural way, and we must take pains to state them definitely, since they have a great influence on what follows. For the beginning is thought to be more than half of the whole, and many of the questions we ask are cleared up by it.

Book I, 1098a-b; §7 as translated by W. D. Ross

For some identify happiness with virtue, some with practical wisdom, others with a kind of philosophic wisdom, others with these, or one of these, accompanied by pleasure or not without pleasure; while others include also external prosperity. Now … it is not probable that these should be entirely mistaken, but rather that they should be right in at least some one respect or even in most respects.

Book I, 1098b.23

For pleasure is a state of soul, and to each man that which he is said to be a lover of is pleasant.... Now for most men their pleasures are in conflict with one another because these are not by nature pleasant, but the lovers of what is noble find pleasant the things that are by nature pleasant; and virtuous actions are such... Happiness then is the best, noblest, and most pleasant thing in the world, and these attributes are not severed as in the inscription at Delos: Most noble is that which is justest, and best is health; but pleasantest is it to win what we love.

Book I, 1099a.6

Everything that depends on the action of nature is by nature as good as it can be, and similarly everything that depends on art or any rational cause, and especially if it depends on the best of all causes. To entrust to chance what is greatest and most noble would be a very defective arrangement.

The truly good and wise man will bear all kinds of fortune in a seemly way, and will always act in the noblest manner that the circumstances allow.

Book I, 1101a

May not we then confidently pronounce that man happy who realizes complete goodness in action, and is adequately furnished with external goods? Or should we add, that he must also be destined to go on living not for any casual period but throughout a complete lifetime in the same manner, and to die accordingly, because the future is hidden from us, and we conceive happiness as an end, something utterly and absolutely final and complete? If this is so, we shall pronounce those of the living who possess and are destined to go on possessing the good things we have specified to be supremely blessed, though on the human scale of bliss.

For legislators make the citizens good by forming habits in them, and this is the wish of every legislator, and those who do not effect it miss their mark, and it is in this that a good constitution differs from a bad one.

Book II, 1103b.4

.... In a word, acts of any kind produce habits or characters of the same kind. Hence we ought to make sure that our acts are of a certain kind; for the resulting character varies as they vary. It makes no small difference, therefore, whether a man be trained in his youth up in this way or that, but a great difference, or rather all the difference.

Book II, 1103b

It is well said, then, that it is by doing just acts that the just man is produced, and by doing temperate acts the temperate man; without doing these no one would have even a prospect of becoming good. But most people do not do these, but take refuge in theory and think they are being philosophers and will become good in this way, behaving somewhat like patients who listen attentively to their doctors, but do none of the things they are ordered to do.

Book II, 1105b.9

Again, it is possible to fail in many ways (for evil belongs to the class of the unlimited … and good to that of the limited), while to succeed is possible only in one way (for which reason also one is easy and the other difficult—to miss the mark easy, to hit it difficult); for these reasons also, then, excess and defect are characteristic of vice, and the mean of virtue; For men are good in but one way, but bad in many.

Book II, 1106b.28

The vices respectively fall short of or exceed what is right in both passions and actions, while virtue both finds and chooses that which is intermediate.

Book II, 1107a.4

Variant: Some vices miss what is right because they are deficient, others because they are excessive, in feelings or in actions, while virtue finds and chooses the mean.

In cases of this sort, let us say adultery, rightness and wrongness do not depend on committing it with the right woman at the right time and in the right manner, but the mere fact of committing such action at all is to do wrong.

Any one can get angry — that is easy — or give or spend money; but to do this to the right person, to the right extent, at the right time, with the right motive, and in the right way, that is not for every one, nor is it easy.

Book II, 1109a.27.

Variant translation: Anybody can become angry, that is easy; but to be angry with the right person, and to the right degree, and at the right time, for the right purpose, and in the right way, that is not within everybody's power and is not easy.

As quoted in The Child: At Home and School (1944) by Edith M. Leonard, Lillian E. Miles, and Catherine S. Van der Kar, p. 203

Therefore only an utterly senseless person can fail to know that our characters are the result of our conduct.

Book III, 5.12

Variant: Now not to know that it is from the exercise of activities on particular objects that states of character are produced is the mark of a thoroughly senseless person.

μεταβολὴ δὲ πάντων γλυκύ

Change in all things is sweet.

Book VII, 14

Remark: While this quote is known as Aristotle's, he did not propose it as his own saying, but as a citation from another author. The full text is: "But 'change in all things is sweet', as the poet says, because of some vice."

ἄνευ γὰρ φίλων οὐδεὶς ἕλοιτ᾽ ἂν ζῆν, ἔχων τὰ λοιπὰ ἀγαθὰ πάντα

Without friends no one would choose to live, though he had all other goods.

Book VIII, 1155a.5

When people are friends, they have no need of justice, but when they are just, they need friendship in addition.

Book VIII, 1155a.26

The best friend is he that, when he wishes a person's good, wishes it for that person's own sake.

Book IX, 1168b.1

Variants: My best friend is the man who in wishing me well wishes it for my sake.The best friend is the man who in wishing me well wishes it for my sake.

After these matters we ought perhaps next to discuss pleasure. For it is thought to be most intimately connected with our human nature, which is the reason why in educating the young we steer them by the rudders of pleasure and pain; it is thought, too, that to enjoy the things we ought and to hate the things we ought has the greatest bearing on virtue of character. For these things extend right through life, with a weight and power of their own in respect both to virtue and to the happy life, since men choose what is pleasant and avoid what is painful; and such things, it will be thought, we should least of all omit to discuss, especially since they admit of much dispute.

Book X, 1172a.17

And happiness is thought to depend on leisure; for we are busy that we may have leisure, and make war that we may live in peace.

Book X, 1177b.4

Now the activity of the practical virtues is exhibited in political or military affairs, but the actions concerned with these seem to be unleisurely. Warlike actions are completely so (for no one chooses to be at war, or provokes war, for the sake of being at war; any one would seem absolutely murderous if he were to make enemies of his friends in order to bring about battle and slaughter); but the action of the statesman is also unleisurely, and-apart from the political action itself—aims at despotic power and honours, or at all events happiness, for him and his fellow citizens—a happiness different from political action, and evidently sought as being different. So if among virtuous actions political and military actions are distinguished by nobility and greatness, and these are unleisurely and aim at an end and are not desirable for their own sake, but the activity of reason, which is contemplative, seems both to be superior in serious worth and to aim at no end beyond itself, and to have its pleasure proper to itself (and this augments the activity), and the self-sufficiency, leisureliness, unweariedness (so far as this is possible for man), and all the other attributes ascribed to the supremely happy man are evidently those connected with this activity, it follows that this will be the complete happiness of man, if it be allowed a complete term of life.

Further, the state is by nature clearly prior to the family and to the individual, since the whole is of necessity prior to the part; for example, if the whole body be destroyed, there will be no foot or hand, except in an equivocal sense, as we might speak of a stone hand; for when destroyed the hand will be no better than that. But things are defined by their working and power; and we ought not to say that they are the same when they no longer have their proper quality, but only that they have the same name.

Book I, Part II

The proof that the state is a creation of nature and prior to the individual is that the individual, when isolated, is not self-sufficing; and therefore he is like a part in relation to the whole.

Book I, Part II

He who is unable to live in society, or who has no need because he is sufficient for himself, must be either a beast or a god.

Book I, 1253a.27

Man, when perfected, is the best of animals, but when separated from law and justice, he is the worst of all.

Book I, 1253a.31

Money was intended to be used in exchange, but not to increase at interest. And this term interest, which means the birth of money from money, is applied to the breeding of money because the offspring resembles the parent. Wherefore of all modes of getting wealth this is the most unnatural.

Book I, 1258b.4

Men … are easily induced to believe that in some wonderful manner everybody will become everybody's friend, especially when some one is heard denouncing the evils now existing in states, suits about contracts, convictions for perjury, flatteries of rich men and the like, which are said to arise out of the possession of private property. These evils, however, are due to a very different cause — the wickedness of human nature.

Book II, 1263b.15

One would have thought that it was even more necessary to limit population than property; and that the limit should be fixed by calculating the chances of mortality in the children, and of sterility in married persons. The neglect of this subject, which in existing states is so common, is a never-failing cause of poverty among the citizens; and poverty is the parent of revolution and crime.

The good citizen need not of necessity possess the virtue which makes a good man.

Book III, 1276b.34

A state is not a mere society, having a common place, established for the prevention of mutual crime and for the sake of exchange.... Political society exists for the sake of nobleactions, and not of mere companionship.

It is also in the interests of a tyrant to make his subjects poor, so that he may be able to afford the cost of his bodyguard, while the people are so occupied with their daily tasks that they have no time for plotting.

Book V, 1313b.16

... καὶ ἡ εἰσφορὰ τῶν τελῶν...

Subjects are also kept poor by payment of taxes.

Book V, 1313b.16

A tyrant must put on the appearance of uncommon devotion to religion. Subjects are less apprehensive of illegal treatment from a ruler whom they consider god-fearing and pious. On the other hand, they do less easily move against him, believing that he has the gods on his side.

Happiness, whether consisting in pleasure or virtue, or both, is more often found with those who are highly cultivated in their minds and in their character, and have only a moderate share of external goods, than among those who possess external goods to a useless extent but are deficient in higher qualities.

Book VII, 1323b.1

But that the unequal should be given to equals, and the unlike to those who are like, is contrary to nature, and nothing which is contrary to nature is good.

Those who live in a cold climate and in [northern] Europe are full of spirit, but wanting in intelligence and skill; and therefore they keep their freedom, but have no political organization, and are incapable of ruling over others. Whereas the natives of Asia are intelligent and inventive, but they are wanting in spirit, and therefore they are always in a state of subjection and slavery. But the Hellenic race, which is situated between them, is likewise intermediate in character, being high-spirited and also intelligent. Hence it continues free, and is the best governed of any nation, and, if it could be formed into one state, would be able to rule the world.

Let us then enunciate the functions of a state and we shall easily elicit what we want: First there must be food; secondly, arts, for life requires many instruments; thirdly, there must be arms, for the members of a community have need of them, and in their own hands, too, in order to maintain authority both against disobedient subjects and against external assailants....

Book VII, 1328b.4

The appropriate age for marriage is around eighteen for girls and thirty-seven for men.

Book VII, 1335a.27

It is not easy to determine the nature of music, or why any one should have a knowledge of it.

Book VIII, Part V

There can be no doubt that children should be taught those useful things which are really necessary, but not all things, for occupations are divided into liberal and illiberal; and to young children should be imparted only such kinds of knowledge as will be useful to them without vulgarizing them. And any occupation, art, or science which makes the body, or soul, or mind of the freeman less fit for the practice or exercise of virtue is vulgar; wherefore we call those arts vulgar which tend to deform the body, and likewise all paid employments, for they absorb and degrade the mind. There are also some liberal arts quite proper for a freeman to acquire, but only in a certain degree, and if he attend to them too closely, in order to attain perfection in them, the same evil effects will follow.

For well-being and health, again, the homestead should be airy in summer, and sunny in winter. A homestead possessing these qualities would be longer than it is deep; and its main front would face the south.

It is absurd to hold that a man ought to be ashamed of being unable to defend himself with his limbs but not of being unable to defend himself with speech and reason, when the use of reason is more distinctive of a human being than the use of his limbs.

Book I, 1355b.1

Evils draw men together.

Book I, 1362b.39: quoting a proverb

Thus every action must be due to one or other of seven causes: chance, nature, compulsion, habit, reasoning, anger, or appetite.

Book I, 1369a.5

Variant: All human actions have one or more of these seven causes: chance, nature, compulsions, habit, reason, passion and desire

The young have exalted notions, because they have not been humbled by life or learned its necessary limitations; moreover, their hopeful disposition makes them think themselves equal to great things—and that means having exalted notions. They would always rather do noble deeds than useful ones: Their lives are regulated more by moral feeling than by reasoning.... All their mistakes are in the direction of doing things excessively and vehemently. They overdo everything; they love too much, hate too much, and the same with everything else.

Book II, 1389a.31

Wit is cultured insolence.

Book II, 1389b.11

It is simplicity that makes the uneducated more effective than the educated when addressing popular audiences.

I have gained this by philosophy … I do without being ordered what some are constrained to do by their fear of the law.

Liars … when they speak the truth they are not believed.

Hope is the dream of a waking man.

p. 187.

A friend is one soul abiding in two bodies.

p. 188; also reported in various sources as:
Friendship is a single soul dwelling in two bodies.
A true friend is one soul in two bodies.
Love is composed of a single soul inhabiting two bodies.
What is a friend? A single soul dwelling in two bodies.

A similar statement was attributed to Aristotle in antiquityː "Φίλος μὲν Σωκράτης, ἀλλὰ φιλτέρα ἀλήθεια." ["Socrates is a friend, but truth is a greater."] — Ammonius Hermiae, Life of Aristotle (as translated in Dictionary of Quotations (1906) by Thomas Benfield Harbottle, p. 527). The variant mentioned above may possibly be derived from a reduction of a statement known to have been made by Isaac Newton, who at the head of notes he titled Quaestiones Quaedam Philosophicae (Certain Philosophical Questions) wrote in Latin: "Amicus Plato— amicus Aristoteles— magis amica veritas" which translates to: "Plato is my friend— Aristotle is my friend— but my greatest friend is truth." (c. 1664)

Another possible origin of the "dear is Plato" statement is in the Nicomachean Ethics; the Ross translation (of 1096a.11–1096a.16) provides: "We had perhaps better consider the universal good and discuss thoroughly what is meant by it, although such an inquiry is made an uphill one by the fact that the Forms have been introduced by friends of our own. Yet it would perhaps be thought to be better, indeed to be our duty, for the sake of maintaining the truth even to destroy what touches us closely, especially as we are philosophers; for, while both are dear, piety requires us to honour truth above our friends."
Note that the last clause, when quoted by itself loses the connection to "the friends" who introduced "the Forms", Plato above all. Therefore the misattribution could be the result of the "quote" actually being a paraphrase which identifies Plato where Aristotle only alludes to him circumspectly.

The single harmony produced by all the heavenly bodies singing and dancing together springs from one source and ends by achieving one purpose, and has rightly bestowed the name not of "disordered" but of "ordered universe" upon the whole.

Remember that time slurs over everything, let all deeds fade, blurs all writings and kills all memories. Except are only those which dig into the hearts of men by love.

"The Letter of Aristotle to Alexander on the Policy toward the Cities", translated from Lettre d’Aristote à Alexandre sur la politique envers les cités, an Arabic text translated and edited by Józef Bielawski and Marian Plezia (1970), p. 72; translated from an ancient Greek text that survived only in Arabic translation, there is little acceptance that this is an authentic letter of Aristotle.

It is the mark of an educated mind to be able to entertain a thought without accepting it.

An interpretative gloss of Aristotle's position in Nicomachean Ethics book 1 section 9, tacitly inserted by J. A. K. Thomson in his English translation The Ethics of Aristotle (1955). The original Greek at Book I 1099b.29, reads ὁμολογούμενα δὲ ταῦτ’ ἂν εἴη καὶ τοῖς ἐν ἀρχῇ, which W. D. Ross translates fairly literally as [a]nd this will be found to agree with what we said at the outset. Thomson's much freer translation renders the same passage thus: [t]he conclusion that happiness depends upon ourselves is in harmony with what I said in the first of these lectures; the words "that happiness depends upon ourselves" were added by Thomson to clarify what "the conclusion" is, but they do not appear in the original Greek of Aristotle.[1] Rackham's earlier English translation added a similar gloss, but averted confusion by confining it to a footnote.[2]

We are what we repeatedly do. Excellence, then, is not an act, but a habit.

Variant: We are what we repeatedly do, therefore excellence is not an act, but a habit.

Source: Will Durant, The Story of Philosophy: The Lives and Opinions of the World's Greatest Philosophers (1926) [Simon & Schuster/Pocket Books, 1991, ISBN 0-671-73916-6], Ch. II: Aristotle and Greek Science; part VII: Ethics and the Nature of Happiness: "Excellence is an art won by training and habituation: we do not act rightly because we have virtue or excellence, but we rather have these because we have acted rightly; 'these virtues are formed in man by his doing the actions'; we are what we repeatedly do. Excellence, then, is not an act but a habit: 'the good of man is a working of the soul in the way of excellence in a complete life... for as it is not one swallow or one fine day that makes a spring, so it is not one day or a short time that makes a man blessed and happy'" (p. 76). The quoted phrases within the quotation are from the Nicomachean Ethics, Book II, 4; Book I, 7. The misattribution is from taking Durant's summation of Aristotle's ideas as being the words of Aristotle himself.

We live in deeds, not years; in thoughts not breaths; // In feelings, not in figures on a dial. // We should count time by heart throbs. He most lives // Who thinks most, feels the noblest, acts the best.

This is actually from the poem "We live in deeds..." by Philip James Bailey. This explains the strange pattern of capitalization.

The worst form of inequality is to try to make unequal things equal.

This first appears in 1974 in an explanation of Aristotle's politics in Time magazine, before being condensed to an epigram as "Aristotle's Axiom" in Peter's People (1979) by Laurence J. Peter

There is only one way to avoid criticism: do nothing, say nothing and be nothing.

Source: Elbert Hubbard, Little Journeys to the Homes of American Statesmen (1898), p. 370: "If you would escape moral and physical assassination, do nothing, say nothing, be nothing—court obscurity, for only in oblivion does safety lie." Other versions of the saying were repeated in several of Hubbard's later writings.

Suffering becomes beautiful when anyone bears great calamities with cheerfulness, not through insensibility but through greatness of mind.

Widely attributed since the mid to late 19th century, this apparently derives from a gloss or commentary on the following passage from Aristotle's Nicomachean Ethics (c. 325 BC), Book 1, Ch. XI (Bekker No. 1100b.13–14):

But nevertheless, even in these [misfortunes], nobility of the soul is conspicuous, when a man bears and digests many and great misfortunes, not from insensibility, but because he is high spirited and magnanimous. But if the energies are the things that constitute the bliss or the misery of life, as we said, no happy man can ever become miserable.

Nevertheless even under these [misfortunes] the force of nobility shines out, when a man bears calmly many great disasters, not from insensibility, but because he is generous and of a great soul. Setting happiness then, as we do, not in the outward surroundings of man, but in his inward state, we may fairly say that no one who has attained to the bliss of virtue will ever justly become an object of pity or contempt.

St. George William Joseph Stock, Lectures in the Lyceum or Aristotle's ethics for English readers (1897), p. 47

Those who can, do, those who cannot, teach.

This and many similar quotes with the same general meaning are misattributed to Aristotle as a result of Twitter attribution decay. The original source of the quote remains anonymous. The oldest reference resides in the works of George Bernard Shaw, Man and Superman (1903): "Maxims for Revolutionists", where he claims that “He who can, does. He who cannot, teaches.”.

Humour is the only test of gravity, and gravity of humour. For a subject which would not bear raillery is suspicious; and a jest which would not bear a serious examination is certainly false wit.

Robert [Grosseteste] became much interested in science and scientific method... He was conscious of the dual approach by means of induction and deduction (resolution and composition); i.e., from the empirical knowledge one proceeds to probable general principles, and from these as premises one them derives conclusions which constitute verifications or falsifications of the principles. This approach to science was not that far removed from Aristotle...

[Aristotle] totally misrepresents Plato's doctrine of "Ideas." … It is also pertinent to inquire, what is the difference between the "formal cause" of Aristotle and the archetypal ideas of Plato? … Yet Aristotle is forever congratulating himself that he alone has properly treated the "formal" and the "final cause"!

According to Aristotle, scientific investigation and explanation was a twofold process, the first inductive and the second deductive. The investigator must begin with what was prior in the order of knowing, that is, with the facts observed through the senses, and he must ascend through induction to generalizations or universal forms or causes which were most remote from sensory experience, yet causing that experience and therefore prior in the order of nature. [Footnote:] The idea that the order of demonstration was the order of nature came from Plato. Aristotle said that the order of discovery was the reverse of the order of demonstration.

A. C. Crombie, Robert Grosseteste and the Origins of Experimental Science (1953)

The model of scientific knowledge, in which effects could be shown to follow necessarily from their causes as conclusions from premises, Aristotle held to be mathematics, and where mathematics could be used in the natural sciences their conclusions were also exact and necessary. ... Of the inductive process by which the investigator passed from sensory experience of particular facts or connexions to a grasp of the prior demonstrative principles that explained them, Aristotle gave a clear psychological account. The final stage in the process was the sudden act by which the intuitive reason or νοῦς, after a number of experiences of facts, grasped the universal or theory explaining them, or penetrated to knowledge of the substance causing and connecting them.

It is pretty definitely settled, among men competent to form a judgment, that Aristotle was the best educated man that ever walked on the surface of this earth. He is still, as he was in Dante's time, the "master of those that know." It is, therefore, not without reason that we look to him, not only as the best exponent of ancient education, but as one of the worthiest guides and examples in education generally. That we may not lose the advantage of his example, it will be well, before we consider his educational theories, to cast a glance at his life, the process of his development, and his work.

John Philoponus (c. 490-570) of Alexandria... refuted Aristotle's theory that the velocities of falling bodies in a given medium are proportional to their weight, making the observation that "if one lets fall simultaneously from the same height two bodies differing greatly in weight, one will find that the ratio of the times of their motion does not correspond to the ratios of their weights, but the difference in time is a very small one." …He also criticized Aristotle's antiperistasis theory of projectile motion, which states that the air displaced by the object flows back to push it from behind. Instead Philoponus concluded that "some incorporeal kinetic power is imparted by the thrower to the object thrown" and that "if an arrow or a stone is projected by force in a void, the same will happen much more easily, nothing being necessary except the thrower." This is the famous "impetus theory," which was revived in medieval Islam and again in fourteenth century Europe, giving rise to the beginning of modern dynamics.

John Freely, Before Galileo: The Birth of Modern Science in Medieval Europe (2012)

We have in our age new accidents and observations, and such, that I question not in the least, but if Aristotle were now alive, they would make him change his opinion; which may be easily collected from the very manner of his discoursing: For when he writeth that he e­steemeth the Heavens inalterable, &c. because no new thing was seen to be begot therein, or any old to be dissolved, he seems im­plicitely to hint unto us, that when he should see any such accident, he would hold the contrary; and confront, as indeed it is meet, sensible experiments to natural reason: for had he not made any reckoning of the senses, he would not then from the not seeing of any sensible mutation, have argued immutability.

I do believe for certain, that he [Aristotle] first procured, by the help of the senses, such experiments and observations as he could, to assure him as much as was possible of the conclusion, and that he afterwards sought out the means how to demonstrate it; for this is the usual course in demonstrative sciences. And the reason thereof is, because when the conclusion is true, by the help of the resolutive method, one may hit upon some proposition before demonstrated, or come to some principle known per se; but if the conclusion be false, a man may proceed in infinitum, and never meet with any truth already known.

Aristotle... justly reproves Democritus for saying, that if no medium were interposed, a pismire would be visible in the heavens; asserting, on the contrary, that if vacuity alone intervened, nothing possibly could be seen, because all vision is performed by changes or motions in the organ of sight; and all such changes or motions imply an interposed medium. Between the perceptions of the eye and of the ear there is a striking analogy. Bodies are only visible by their colour; and colour is only perceptible in light; and unless different motions were excited by light in the eye, colour and the distinctions of colour would no more be visible, than, independently of different vibrations communicated to the ear, sound, and the distinctions of sound, would be audible. When the vibrations in a given time are many, the sensation of sharpness or shrillness follows; when the vibrations are, in the same time, comparatively few, the sensation of flatness is the result: but the first sound does not excite many vibrations because it is shrill or sharp, but it is sharp because it excites many vibrations; and the second sound does not excite few vibrations because it is flat or grave, but it is grave because it excites few vibrations.

On the authority of Aristotle... motion in the planetary world was somehow directed by the more perfect motion in higher spheres, and so on, up to the outermost sphere of fixed stars, indistinguishable from the prime mover. This implied a refined animistic and pantheistic world view, incomparably more rational than the ancient world views of Babylonians and Egyptians, among others, but a world view, nonetheless, hardly compatible with the idea of "inertial motion" which is implied in Buridan's concept of "impetus"… a momentous breaking point... which was to bear fruit... in the hands, first of Copernicus and then of Newton.

Julio A. Gonzalo, The Intelligible Universe: An Overview of the Last Thirteen Billion Years (2008) 2nd edn

Time for us embraces a whole field of 'before and after', but Aristotle says: 'Before and after are involved in motion, but time is these so far as they are numbered' (Phys. 223a28). Elsewhere he defines time as 'the number of motion in respect of before and after', and he could seriously discuss the question whether there could be time without conscious and thinking beings; 'for if there could be no one to count, there could be nothing counted. ...If nothing can count but soul, and within soul mind, there cannot be time without soul, but only the substratum of time' (ibid. 219b2, 223a22)

W. K. C. Guthrie, A History of Greek Philosophy Vol. 1, "The Earlier Presocratics and the Pythagoreans" (1962)

As we now know, in the evolution of the structure of human activities, profitability works as a signal that guides selection towards what makes man more fruitful; only what is more profitable will, as a rule, nourish more people, for it sacrifices less than it adds. So much was at least sensed by some Greeks prior to Aristotle. Indeed, in the fifth century - that is, before Aristotle - the first truly great historian began his history of the Peloponnesian War by reflecting how early people `without commerce, without freedom of communication either by land or sea, cultivating no more of their territory than the exigencies of life required, could never rise above nomadic life' and consequently `neither built large cities nor attained to any other form of greatness' (Thucydides, Crawly translation, 1,1,2). But Aristotle ignored this insight.
Had the Athenians followed Aristotle's counsel - counsel blind both to economics and to evolution - their city would rapidly have shrunk into a village, for his view of human ordering led him to an ethics appropriate only to, if anywhere at all, a stationary state. Nonetheless his doctrines came to dominate philosophical and religious thinking for the next two thousand years - despite the fact that much of that same philosophical and religious thinking took place within a highly dynamic, rapidly extending, order.(...) The anti-commercial attitude of the mediaeval and early modern Church, condemnation of interest as usury, its teaching of the just price, and its contemptuous treatment of gain is Aristotelian through and through. (...) Notwithstanding, and indeed wholly neglecting, the existence of this great advance, a view that is still permeated by Aristotelian thought, a naive and childlike animistic view of the world (Piaget, 1929:359), has come to dominate social theory and is the foundation of socialist thought.

Friedrich Hayek, The Fatal Conceit (1988), Ch. 3: The Evolution of the Market: Trade and Civilisation

Current scientific and philosophical usage is so deeply influenced by the Aristotelian tradition, which knows nothing of evolution, that existing dichotomies and contrasts not only usually fail to capture correctly the processes underlying the problems and conflicts discussed in chapter one, but actually hinder understanding of those problems and conflicts themselves.

Unfortunately... the philosophy of Aristotle laid it down as a principle, that the celestial motions were regulated by laws proper to themselves, and bearing no affinity to those which prevail on earth. By thus drawing a broad and impassable line of separation between celestial and terrestrial mechanics, it placed the former altogether out of the pale of experimental research, while it at the same time impeded the progress of the latter by the assumption of principles respecting natural and unnatural motions, hastily adopted from the most superficial and cursory and remark, undeserving even the name of observation. Astronomy therefore continued for ages a science of mere record, in which theory had no part, except in so far as it attempted to conciliate the inequalities of the celestial motions with that assumed law of uniform circular revolution which was alone considered consistent with the perfection of the heavenly mechanism.

In the old philosophy, a curious conjunction of ethical and physical prejudices had led to the notion that there was something ethically bad and physically obstructive about matter. Aristotle attributes all irregularities and apparent dysteleologies in nature to the disobedience, or sluggish yielding, of matter to the shaping and guiding influence of those reasons and causes which were hypostatised in his ideal 'Forms.'

Aristotle was the first accurate critic and truest judge — nay, the greatest philosopher the world ever had; for he noted the vices of all knowledges, in all creatures, and out of many men's perfections in a science he formed still one Art.

Aristotle had not been popular in the ancient world, but his ideas were picked up by the materialistically-minded Arabs as they were developing their culture, and from there his works were introduced into Western Europe. They became the rage, stimulating a whole intellectual revival. It soon became necessary for the church to deal with this point of view, and through the genius of Thomas Aquinas all of the church ideas were rewritten within the framework of Aristotle's ideas with their mythological character reduced to a bare minimum.

Most expositions of Aristotle's doctrines, when they have not been dictated by a spirit of virulent detraction, or unsympathetic indifference, have carefully suppressed all, or nearly all, the absurdities, and only retained what seemed plausible and consistent. But in this procedure their historical significance disappears.

Aristotle... seems utterly destitute of any sense of the Ineffable. There is no quality more noticeable in him than his unhesitating confidence in the adequacy of the human mind to comprehend the universe... He never seems to be visited by misgivings as to the compass of human faculty, because his unhesitating mind is destitute of awe. He has no abiding consciousness of the fact deeply impressed on other minds, that the circle of the Knowable is extremely limited; and that beyond it lies a vast mystery... impenetrable. Hence the existence of Evil is no perplexity to his soul; it is accepted as a simple fact. Instead of being troubled by it, saddened by it, he quietly explains it as the consequence of Nature not having correctly written her meaning. This mystery which has darkened so many sensitive meditative minds with anguish he considered to be only bad orthography.

George Henry Lewes, Aristotle: a Chapter from the History of Science (1864)

Roger Bacon expressed a feeling which afterwards moved many minds, when he said that if he had the power he would burn all the works of the Stagirite, since the study of them was not simply loss of time, but multiplication of ignorance. Yet in spite of this outbreak every page is studded with citations from Aristotle, of whom he everywhere speaks in the highest admiration.

Aristotle, that histrionic mountebank, who from behind a Greek mask has so long bewitched the Church of Christ, that most cunning juggler of souls, who, if he had not been accredited as human blood and bone, we should have been justified in maintaining to be the veritable devil.

Martin Luther, in a letter to John Stuart Blackie, 1516. In Four Phases of Morals (1871)

Aristotle sees no difference between the falling of a leaf or a stone and the death of the good and noble people in the ship; nor does he distinguish between the destruction of a multitude of ants by an ox depositing on them his excrement and the death of worshippers killed by the fall of the house when its foundations give way. In short, the opinion of Aristotle is this: Everything is the result of management which is constant, which does not come to an end and does not change any of its properties, as e.g., the heavenly beings, and everything which continues according to a certain rule... But that which is not constant, and does not follow a certain rule... is due to chance and not to management; it is in no relation to Divine Providence. Aristotle holds that it is even impossible to ascribe to Providence that management of these things. ...It is the belief of those who turned away from our Law and said: "God hath forsaken the earth." (Ezek. ix. 9)

When I saw that Moses’ version of the Genesis of the world did not fit sufficiently in many ways with Aristotle and the rest of the philosophers, I began to have doubts about the truth of all philosophers and started to investigate the secrets of nature.

In his discussion on slavery Aristotle said that when the shuttle wove by itself and the plectrum played by itself chief workmen would not need helpers nor masters slaves. At the time he wrote, he believed that he was establishing the eternal validity of slavery; but for us today he was in reality justifying the existence of the machine. Work, it is true, is the constant form of man's interaction with his environment, if by work one means the sum total of exertions necessary to maintain life; and the lack of work usually means an impairment of function and a breakdown in organic relationship that leads to substitute forms of work, such as invalidism and neurosis. But work in the form of unwilling drudgery or of that sedentary routine which... the Athenians so properly despised—work in these forms is the true province of machines. Instead of reducing human beings to work-mechanisms, we can now transfer the main part of burden to automatic machines. This potentially... is perhaps the largest justification of the mechanical developments of the last thousand years.

The first clear expression of the idea of an element occurs in the teachings of the Greek philosophers. ...Aristotle ...who summarized the theories of earlier thinkers, developed the view that all substances were made of a primary matter... On this, different forms could be impressed... so the idea of the transmutation of the elements arose. Aristotle's elements are really fundamental properties of matter.... hotness, coldness, moistness, and dryness. By combining these in pairs, he obtained what are called the four elements, fire, air, earth and water... a fifth, immaterial, one was added, which appears in later writings as the quintessence. This corresponds with the ether. The elements were supposed to settle out naturally into the earth (below), water (the oceans), air (the atmosphere), fire and ether (the sky and heavenly bodies).

It appears to me that there can be no question, that Aristotle stands forth, not only as the greatest figure in antiquity, but as the greatest intellect that has ever appeared upon the face of this earth.

George J. Romanes, as quoted in "The most important question in the world.": Is mankind advancing? (1910), p. 38

Aristotle, as a philosopher, is in many ways very different from all his predecessors. He is the first to write like a professor: his treatises are systematic, his discussions are divided into heads, he is a professional teacher, not an inspired prophet. His work is critical, careful, pedestrian, without any trace of Bacchic enthusiasm. The Orphic elements in Plato are watered down in Aristotle, and mixed with a strong dose of common sense; where he is Platonic, one feels that his natural temperament has been overpowered by the teaching to which he has been subjected. He is not passionate, or in any profound sense religious. The errors of his predecessors were the glorious errors of youth attempting the impossible; his errors are those of age which cannot free itself of habitual prejudices. He is best in detail and in criticism; he fails in large construction, for lack of fundamental clarity and Titanic fire.

I conclude that the Aristotelian doctrines are wholly false, with the exception of the formal theory of the syllogism, which is unimportant. Any person in the present day who wishes to learn logic will be wasting his time if he reads Aristotle or any of his disciples. Nonetheless, Aristotle’s logical writings show great ability, and would have been useful to mankind if they had appeared at a time when intellectual originality was still active. Unfortunately, they appeared at the very end of the creative period of Greek thought, and therefore came to be accepted as authoritative. By the time that logical originality revived, a reign of two thousand years had made Aristotle very difficult to dethrone. Throughout modern times, practically every advance in science, in logic, or in philosophy has had to be made in the teeth of opposition from Aristotle’s disciples.

Aristotle, so far as I know, was the first man to proclaim explicitly that man is a rational animal. His reason for this view was one which does not now seem very impressive; it was, that some people can do sums.

To modern educated people, it seems obvious that matters of fact are to be ascertained by observation, not by consulting ancient authorities. But this is an entirely modern conception, which hardly existed before the seventeenth century. Aristotle maintained that women have fewer teeth than men; although he was twice married, it never occurred to him to verify this statement by examining his wives' mouths. He said also that children would be healthier if conceived when the wind is in the north. One gathers that the two Mrs. Aristotles both had to run out and look at the weathercock every evening before going to bed. He states that a man bitten by a mad dog will not go mad, but any other animal will (Hiss. Am., 704a); that the bite of the shrewmouse is dangerous to horses, especially if the mouse is pregnant (ibid., 604b); that elephants suffering from insomnia can be cured by rubbing their shoulders with salt, olive oil, and warm water (ibid., 605a); and so on and so on. Nevertheless, classical dons, who have never observed any animal except the cat and the dog, continue to praise Aristotle for his fidelity to observation.

Socrates and Plato had no time for Athenian democracy, and wanted a revived aristocratic government for their city. But both were moral radicals; they thought ordinary morality was radically misguided, and that public opinion should be ignored when it was at odds with one's conscience or reason. Things are very different in Aristotle. Plato's concern for the balance of the soul was shared by Aristotle, but not his ethical radicalism.

Justice is of two kinds, justice in distribution and justice in rectification. … Aristotle thinks primarily of setting things straight, and denies that rectificatory justice contains an element of 'tit for tat'.

Aristotle’s genius was for showing the ways in which we might construct the “best practicable state.” This was not mere practicality; the goals of political life are not wholly mundane. The polity comes into existence for the sake of mere life, but it continues to exist for the sake of the good life. The good life is richly characterized, involving as it does the pursuit of justice, the expansion of the human capacities used in political debate, and the development of all the public and private virtues that a successful state can shelter—military courage, marital fidelity, devotion to the physical and psychological welfare of our children, and so on indefinitely.

Alan Ryan, On Politics: A History of Political Thought: From Herodotus to the Present (2012), Ch. 3 : Aristotle: Politics Is Not Philosophy

Aristotle, who foresaw so many things, never dreamed of the social truth. Cuvier, whose sagacity is so highly lauded, was constrained to yield homage to the genius of Aristotle in Natural History; for myself, who am at this date in full possession of social truth, in politics Aristotle only inspires me with profound pity.

Jules Sandeau, in Money-Bags and Titles: A Hit at the Follies of the Age (1850), Ch. XVIII, p. 185 (said by Timoleon to his father Levrault).

The old Greek philosophy, which in Europe in the later middle ages was synonymous with the works of Aristotle, considered motion as a thing for which a cause must be found: a velocity required a force to produce and to maintain it. The great discovery of Galileo was that not velocity, but acceleration requires a force. This is the law of inertia of which the real content is: the natural phenomena are described by differential equations of the second order.

Men often speak of virtue without using the word but saying instead "the quality of life" or "the great society" or "ethical" or even "square." But do we know what virtue is? Socrates arrived at the conclusion that it is the greatest good for a human being to make everyday speeches about virtue-apparently without ever finding a completely satisfactory definition of it. However, if we seek the most elaborate and least ambiguous answer to this truly vital question, we shall turn to Aristotle's Ethics. There we read among other things that there is a virtue of the first order called magnanimity—the habit of claiming high honors for oneself with the understanding that one is worthy of them. We also read there that sense of shame is not a virtue: sense of shame is becoming for the young who, due to their immaturity, cannot help making mistakes, but not for mature and well-bred men who simply always do the right and proper thing. Wonderful as all this is-we have received a very different message from a very different quarter.

Leo Strauss, "Niccolo Machiavelli", in History of Political Philosophy (3rd ed., 1987) edited by Leo Strauss and Joseph Cropsey

Aristotle especially, both by speculation and observation... reached something like the modern idea of a succession of higher organizations from lower, and made the fruitful suggestion of "a perfecting principle" in Nature. With the coming in of Christian theology this tendency toward a yet truer theory of evolution was mainly stopped, but the old crude view remained...

As man loses touch with his 'inner being', his instinctive depths, he finds himself trapped in the world of consciousness, that is to say, in the world of other people. Any poet knows this truth; when other people sicken him, he turns to hidden resources of power inside himself, and he knows then that other people don't matter a damn. He knows the 'secret life' inside him is the reality; other people are mere shadows in comparison. but the 'shadows' themselves cling to one another. 'Man is a political animal', said Aristotle, telling one of the greatest lies in human history. Man has more in common with the hills, or with the stars, than with other men.